Wagon speed-control system



May 7, 1968 D. E. LAMBETH ET AL 3,381,628

WAGON SPEED'CONTROL SYSTEM Filed Sept. 8, 1966 2 Sheets-Sheet 1 IUUlNvENToR W161 ATTORNEY May 7, 1968 D. E. LAMBETH ET AL 3,381,628

WAGON SPEED-CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Sept. 8, 1966 id m wTm. A N L E ME vz M -5%, M e m United States Patent 3,381,628 WAGONSPEED-CONTROL SYSTEM Dennis E. Lambeth, Cheltenham, and Anthony G. L.Shore, Winchcombe, England, assignors to Dowty Technical DevelopmentsLimited, Brockhampton, England, a British company Filed Sept. 8, 1966,Ser. No. 577,987 Claims priority, application Great Britain, Sept. 16,1965, 39,546/65 6 Claims. (Cl. 104-162) This invention relates to asystem for controlling the speed of wagons moving along a railway track.

It is known to control the speeds of wagons moving along a railway trackby a piston and cylinder device which is actuated by a wheel flange andwhich displaces liquid through control valve mechanism in such mannerthat, if a wagon is moving at less than a critical speed, a force causedby high fluid pressure is exerted on the wheel to accelerate the wagon,and if the wagon is moving at greater than the critical speed, a forcecaused by high fluid pressure is exerted on the wheel to retard thewagon. Some of the devices only perform one of these functions and notboth.

According to the present invention a system for controlling the speedsof wagons moving along a railway track, comprises at least one pair ofhydraulic displacement devices fixed to the track so that both devicesexecute contraction and then extension movements, for the most part atleast, together under rolling engagement by one at least of a pair ofco-axial wagon wheels, and control valve mechanism providingcontrollable connections between each device and either a low pressureliquid source or a high pressure liquid source, said mechanism includinga speed-sensing valve responsive to the flow rate of liquid dischargedby contraction of a first one of said devices, the speed-sensing valveacting when the flow rate is less than a pre-determined value to causeliquid discharged by both devices to flow to the low pressure source,and acting when the flow rate exceeds the pre-determined value to causeliquid discharged by both devices to flow to the high pressure source,and a position-sensing valve including operating means responsive to thequantity of liquid flowing from and to the second of said devices, theoperating means acting on the position-sensing valve substantially uponcompletion of liquid discharge from the second device to the lowpressure source, to connect both devices to the high pressure source,and acting substantially upon completion of the ensuing high pressureliquid flow into the second device to isolate the high pressure sourcefrom both devices.

The first and second hydraulic displacement devices, which may take theform of pistons mounted in cylinders, may be mounted against therespective rails at the same position in the normal direction of travelof a wagon so that both execute con-traction and extension movementssubstantially together. However, the second of the devices may be spaceda small distance from the first in the direction of travel so that thecontraction and extension sequence of the first device starts beforethat of the second device, but that for the most part the sequencesoverlap in time. The purpose of this spacing is to reduce the risk oflifting a lightly loaded wagon since the initial application of forcesgenerated by high fluid pressure do not occur simultaneously.

It the devices are spaced apart, it is possible to mount both against asingle rail for rolling engagement by only one wheel.

In the accompanying drawings:

FIGURE 1 is a plan view of a length of railway track fitted with a wagonspeed control system in accordance with the invention,

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FIGURE 2 is an enlarged sectional View on the line II-II of FIGURE 1showing an installed piston and cylinder device,

FIGURES 3 and 4 are diagrams of control valve mechanism showingdifferent stages of operation at low wagon speeds, and

FIGURE 5 is a diagram of the control valve mechanism showing differentstages of operation at higher wagon speeds.

FIGURE 1 shows two hydraulic displacement devices formed as piston andcylinder devices 11 and 13 secured to the inner side of the left handrail 6 at spaced-apart positions, and two similarly spaced devices 12and 14 secured to the inner side of the right hand rail 7. The spacingof the second device 12 from the first device 11, and of the device 14from the device 13, in the direction of travel of a wagon may be a shortdistance of four inches or thereabouts, for the purpose referred to butthe spacing of the pair of devices 13, 14 from the pair of devices 11,12 is greater so that a pair of wagon wheels having a common rotationalaxis leave the devices 11, 12 before engaging the devices 13, 14.

Each piston and cylinder device has a variable volume chamber filledwith liquid, the chambers of the devices 11 and 13 being connected inparallel by a pipe 15 to control valve mechanism 17, and the chambers ofthe devices 12 and 14 being connected in parallel by a pipe 16 to thecontrol valve mechanism 17. The latter is also connected by a branchpipe 18 to a high pressure main 8, and by a branch pipe 19 to a lowpressure main 9'.

FIGURE 2 shows the mounting of the cylinder of the first device 11 in agenerally upright position against the rail, and a piston head 10 whichis engaged by the flange of a wagon wheel 20 so that the head isdepressed to the position 10', and then rises to its uppermost position10 as the wheel 20 rolls over the device.

In FIGURE 3, the pipe 15 is connected through the body of the valvemechanism 17 to a speed-sensing valve 22 and a high pressure reliefvalve 31, both of which can discharge to the low pressure branch pipe19. The pipe 15 is also connected through a non-return valve 29 to thehigh pressure branch pipe 18. The speed-sensing valve 22 is formed as ahollow plunger which is loaded against a stop 38 by a spring 28 to opena connection through orifices 21 in the plunger, between the pipe 15 anda bore 39 to which the low pressure branch pipe 19 is connected. Therelief valve 31 is formed as a piston which is loaded by a spring 41 toclose orifices 42 in a cylinder-like valve housing 43. The effectivearea over which fluid pressure acts is that of the piston rod 44 becausethere is a hole 45 across the piston itself.

The pipe 16 is connected to a bore 46 containing a dummy piston 23, andto a high pressure relief valve 33. The pipe 16 is also connectedthrough a non-return valve 32 to the high pressure branch pipe 18. Thefluid displacement of the dummy piston 23 over its total travel issubstantially equal to that of each of the piston and cylinder devices12, 14. In its upper position in the drawing, the dummy piston 23 justcloses a passage 27 leading from the bore 46 to the speed sensing valve.In its lower position, the dummy piston 23 closes another passage 47which leads from the bore 46 to a second orifice 48 in the speed sensingvalve 22. A friction ring 40 is mounted in the piston 23 to engage thebore 46. A port 30 is formed in the wall of the dummy piston 23 toconnect the underside of the piston to the passage 27 when the pistondescends. The dummy piston 23, moreover, constitutes operating means fora high pressure valve which consists of a ported sleeve 25 slidable on aported spigot 49. The final downward movement of the dummy piston 23opens the high pressure valve to supply of fluid from the pipe 18, andthe final upward movement closes the high pressure valve. A tappet 5t)formed in the dummy piston 23 for shifting the sleeve valve 25 on itsdownward stroke is preferably formed as a spring device, while a springdetent may act between the ported spigot 49 and the ported sleeve 25,whereby the ported sleeve will move rapidly when the spring forceovercomes the detent force.

The high pressure relief valve 33 is of generally similar constructionto the high pressure relief valve 31. It comprises a piston which isloaded by the spring 28 to close orifices 51 in a cylinder-like valvehousing 52. The effective area over which fluid pressure acts is that ofthe piston rod 53 because there is a hole 54 across the piston itself.In this valve 35, however, there is a stop 55 against opposite sides ofwhich thc piston 33 and the housing 53 are urged by a spring 56 whichacts between the piston and the housing. This valve is operable under anexcess of pressure in the pipe 19 over that in the pipe 16 as anon-return valve, since low fluid pressure can act over the annular areaof the housing 52 between the bore 39 and the stem 53 to move thehousing 52 against the load of the spring 56 until the orifices 51 areuncovered by movement past the piston 33.

The operating sequence of the control valve mechanism under theinfluence of a pair of concentric wagon wheels which roll slowly overthe piston and cylinder devices 11 and 12 will now be described withreference to FIG- URES 3 and 4.

When the flange of a wagon wheel engages the first piston and cylinderdevice 11, hydraulic liquid is expelled from the pipe 15 through theorifices 21 of the speedsensing valve 22 to the low pressure pipe 19,FIGURE 3. The pressure difference across the orifices 21, which acts onthe valve 22 is not sufiicient to overcome the load of the spring 28,and the valve remains unaffected throughout the contraction stroke ofthe piston and cylinder device 11 because the maximum flow occurs at thebeginning of the stroke. At only a short interval after the first evice11 starts to contract, the flange of a concentric wheel on the otherrail engages, and starts to contract, the second device 12. Hydraulicliquid then expelled from the pipe 16 displaces the dummy piston 23downwardly, so that liquid on the underside of this piston passesthrough the second orifice 48 in the valve 22 to the low pressure pipe19.

Near the end of the contraction stroke of the second device 12, that is,at about the time the first device 11 is fully contracted and startingto extend, the dummy piston 23 shifts the ported sleeve valve 25 on theported spigot 49 to connect the high pressure in pipe 18 to theunderside of the dummy piston 23, FIGURE 4. High pressure liquid nowflows through the wall port 36 of the dummy piston 23 and the passage 27to the pipe 15, causing the speed-sensing valve 22 to close, so that thefirst device 11 extends in contact with the wheel flange under highfluid pressure. High fluid pressure is also transmitted by the dummypiston 23 to the pipe 16, so that the device 12 extends in contact withthe other wheel flange. Near the end of the extension stroke of thesecond device 12, that is, at about the time the first device 11 isfully extented, the dummy piston 23 lifts the sleeve valve 25 to cut offthe supply of high pressure from both devices 11 and 12. Thus it is seenthat the devices 11 and 12 are contracted by the respective wheelsagainst low liquid pressure which exerts little, if any, appreciableresistance to movement of the wheels, but that the devices extend underhigh liquid pressure to exert an acceleration force against the wheels.During the sequence described, the devices 13 and 14 remain fullyextended.

At a critical wheel speed along the rail, a pro-determined rate ofinitial flow from the first device 11 causes a pressure drop across theorifices 21 which balances the load of the spring 28. If therefore thespeed of a wagon is above the critical value, liquid expelled from thefirst device 11 through the pipe 15 at the beginning of the contractionstroke, closes the speed-sensing valve 22, as

shown in the full line position in FIGURE 5. The liquid is then expelledthrough the non-return valve 29 to the high pressure pipe 18 and, athigh flow rates, also through the orifices 42 of the high pressurerelief valve 31. When, after a short interval, the second device 12starts to contract, the expelled liquid cannot displace the dummy piston23 because the passage 47 to the speed-sensing valve 22 is closed.Expelled liquid flows instead through the non-return valve 32 to thehigh pressure pipe 18 and, at high flow rates, also through the orifices51 of the high pressure relief valve 33 to the low pressure pipe. Thesleeve valve 25 remains raised and closing the high pres sure connectionof the pipe 18 throughout the contraction stroke of the second device12. When the first device 11 starts to extend, pressure falls in thepipe 15 so that the Speed-sensing valve 22 can open as shown by thechain dot position in FIGURE 5. Low pressure liquid now flows from thepipe 19, through the bore 39 and the orifices 21 into the pipe 15. Thevalve 33 then operates as a non-return valve under low pressure in thepipe 19, whereby the housing 52 lifts against the load of the spring 56to allow low pressure liquid to flow through the orifices 51 and towardsthe pipe 16. If the dummy piston is not in its uppermost position, itwill be raised by liquid from the passage 47 under the pressuredifference across the valve 33.

Thus, it is seen that the devices 11 and 12 are contracted by therespective wheels against high liquid pressure resistance so that aretarding force is exerted against the flanges of the wheels, but thatextension of the devices takes place under low liquid pressure so thatthere is no appreciable acceleration force exerted.

Upon completion of the extension sequence of the devices 11 and 12, thecontrol valve mechanism is restored to the state of readiness shown inFIGURE 1, for responding to movement of the devices 13 and 14.

In practice, there will be some variation in flange depth of the wagonwheels causing a corresponding variation in the hydraulic displacementof the second device 12. It is therefore arranged that under low speedoperation, when the dummy piston 23 moves downwardly, it will alwaysmove far enough to open the high pressure valve 25, 49. Any excess ofliquid displaced will be discharged through the high pressure reliefvalve 33. If subsequently the piston 23 reaches its uppermost positionslightly before extension of the second device 12 is complete, therewill be a fall of pressure in the pipe 16 which allows this extension tobe completed under low pressure liquid flowing through the valve 33.Thus it is seen that the dummy piston 23 is maintained in correct phase.

A small hole 60 is formed in the dummy piston 23 to pass any long termleakage from the non-return valve 32, when the system is not operating,so that such leakage can flow to the passage 47 and thence to lowpressure without depressing the piston 23.

We claim as our invention:

1. A system for controlling the speeds of wagons moving along a railwaytrack, comprising at least one pair of hydraulic displacement devicesfixed to the track so that both devices execute contraction and thenextension movements, for the most part at least, together under rollingengagement by a pair of co-axial wagon wheels, and control valvemechanism providing controllable connections between each device andeither a low pressure liquid source or a high pressure liquid source,said mechanism including a speed-sensing valve responsive to the flowrate of liquid discharge by contraction of a first one of said devices,the speed-sensing valve acting when the flow rate is less than apre-determined value to cause liquid discharged by both devices to flowto the low pressure source, and acting when the flow rate exceeds thepredetermined value to cause liquid discharged by both devices to flowto the high pressure source, and a positionsensing valve includingoperating means responsive to the quantity of liquid flowing from and tothe second of said devices, the operating means acting on theposition-sensing valve substantially upon completion of liquid dischargefrom the second device to the low pressure source, to connect bothdevices to the high pressure source, and acting substantially uponcompletion of the ensuing high pressure liquid flow into the seconddevice to isolate the high pressure source from both devices.

2. A system according to claim '1, wherein the first device is fixedwith respect to one rail and the second device is fixed with respect toanother rail for engagement by the respective Wheels of the pair, thesecond device being spaced from the first device in the normal directionof travel of the Wagon.

3. A system according to claim 1, wherein the operating means for theposition-sensing valve comprises a piston which is movable in a cylinderbore and which transmits pressure between liquid on one side flowingfrom or to the second device, and liquid on the other side flowingrespectively to the low pressure source or from the high pressuresource.

4. A system according to claim 3, wherein the closing of thespeed-sensing valve provides a hydraulic lock which prevents movement ofthe piston by liquid discharge during contraction of the second device,and wherein the connection through which discharge liquid then flows tothe high pressure source is provided by a non-return valve.

5. A system according to claim 1, wherein a high pressure relief valveis interposed between each device and the low pressure source.

6. A system according to claim 5, wherein extension of both devices byliquid from the low pressure source takes place by reverse liquid flowthrough the speed-sensing valve to the first device, and by reverseliquid flow through one of the relief valves to the second device, thisrelief valve being arranged to operate under reverse flow as a lowpressure non-return valve.

References Cited UNITED STATES PATENTS 3,107,633 10/1963 Bick l041623,128,721 4/1964 McGowan 104-162 3,148,633 9/1964 Bick l04162 ARTHUR L.LA POINT, Primary Examiner.

D. F. WORTH, Assistant Examiner.

1. A SYSTEM FOR CONTROLLING THE SPEEDS OF WAGONS MOVING ALONG A RAILWAYTRACK, COMPRISING AT LEAST ONE PAIR OF HYDRAULIC DISPLACEMENT DEVICESFIXED TO THE TRACK SO THAT BOTH DEVICES EXECUTE CONTRACTION AND THENEXTENSION MOVEMENTS, FOR THE MOST PART AT LEAST, TOGETHER UNDER ROLLINGENGAGEMENT BY A PAIR OF CO-AXIAL WAGON WHEELS, AND CONTROL VALVEMECHANISM PROVIDING CONTROLLABLE CONNECTIONS BETWEEN EACH DEVICE ANDEITHER A LOW PRESSURE LIQUID SOURCE OR A HIGH PRESSURE LIQUID SOURCE,SAID MECHANISM INCLUDING A SPEED-SENSING VALVE RESPONSIVE TO THE FLOWRATE OF LIQUID DISCHARGE BY CONTRACTION OF A FIRST ONE OF SAID DEVICES,THE SPEED-SENSING VALVE ACTING WHEN THE FLOW RATE IS LESS THAN APRE-DETERMINED VALUE TO CAUSE LIQUID DISCHARGED BY BOTH DEVICES TO FLOWTO THE LOW PRESSURE SOURCE, AND ACTING WHEN THE FLOW RATE EXCEEDS THEPREDETERMINED VALUE TO CAUSE LIQUID DISCHARGED BY BOTH DEVICES TO FLOWTO THE HIGH PRESSURE SOURCE, AND A POSITIONSENSING VALVE INCLUDINGOPERATING MEANS RESPONSIVE TO THE QUANTITY OF LIQUID FLOWING FROM AND TOTHE SECOND OF SAID DEVICES, THE OPERATING MEANS ACTING ON THEPOSITION-SENSING VALVE SUBSTANTIALLY UPON COMPLETION OF LIQUID DISCHARGEFROM THE SECOND DEVICE TO THE LOW PRESSURE SOURCE, TO CONNECT BOTHDEVICES TO THE HIGH PRESSURE SOURCE, AND ACTING SUBSTANTIALLY UPONCOMPLETION OF THE ENSUING HIGH PRESSURE LIQUID FLOW INTO THE SECONDDEVICE TO ISOLATE THE HIGH PRESSURE SOURCE FROM BOTH DEVICES.